Calculation of energy levels in InGaAs/GaAs quantum dot array

The subbands of the ground state E-c1, the first excited state E-c2 and heavy hole state E-HH1 are calculated by solving the eigenvalues of effective-mass Hamiltonian H-0 which is derived from eight-band k . p theory and the calculations are performed at k(x) = k, = k = 0 for the three-dimensional array of InGaAs/GaAs quantum dots (QDs). With indium content in InGaAs QDs gradually increasing from 30% to 100%,the intersubband transition wavelength of E-c2 to E-c1, blue-shifts from 18.50 to 11.87 mu m,while the transition wavelength of E-c1, to E-HH1, red-shifts from 1. 04 to 1. 73 mu m. With the sizes of Ir-0.5 Ga-0.5 As and InAs QDs increasing from 1.0 to 5.0 nm, the intersubband transition from E-c1, to E-C2 transforms from bound-state-to-continuum-state to bound-state-to-bound-state, and the corresponding intersubband transition wavelengths red-shift from 8.12 pm (5.90 pm) to 53.47 mu m (31.87 pm), respectively, and the transition wavelengths of E-C1 to E-HH1 red-shift from 1. 13 mu m (1.60 mu m) to 1.27 mu m (2.01 mu m), respectively.

Analysis of mode quality factors and mode reflectivities for nanowire cavity by FDTD technique

The mode frequency and the quality factor of nanowire cavities are calculated from the intensity spectrum obtained by the finite-difference time-domain (FDTD) technique and the Pade approximation. In a free-standing nanowire cavity with dielectric constant epsilon = 6.0 and a length of 5 mu m, quality factors of 130, 159, and 151 are obtained for the HE11 modes with a wavelength around 375 nm, at cavity radius of 60, 75, and 90 nm, respectively. The corresponding quality factors reduce to 78, 94, and 86 for a nanowire cavity standing on a sapphire substrate with a refractive index of 1.8. The mode quality factors are also calculated for the TE01 and TM01 modes, and the mode reflectivities are calculated from the mode quality factors.

地热农副产品干燥装置的设计和中间试验

本文根据干燥过程的理论分析和试验研究结果，提出了热风式干燥器设计参数的选择原则，给出一套有一定参考价值的干燥系统的计算方法。该方法概念清楚，不必计算废气排热损失，简化了计算过程。依此，我们设计制造了一套地热干燥中间试验装置，它利用60～70℃的地热水作热源，一次可投湿物料200kg，对于像白菜这类初含水率在90%以上的物料，其每小时最大干燥脱水量超过30kg，平均热效率达到53%。试验结果表明:只有当物料的含水率在90%以上，且表面结合水多的情况下，实际过程才会出现等速干燥阶段。

太阳能空气饱和蒸馏器的试验研究

研究得到了太阳能空气饱和蒸馏器在稳态情况下和不同海水加热温度下的蒸发速度实验式:lgD=7.062+3.446t_0海水加热温度是影响淡水产量的主要因素，以46.2℃为转折，超过此温度，蒸发速度急促增加。液-气两相重量流量比(W/G)，必须与海水加热温度相适应。温度较高，(W/G)值也应较大，这样才能最大限度地提高产水量和降低产水的耗热量。当t_0=96℃时，(W/G)_(最佳)=12;当(W/G)=11时，t_(0最佳)=90℃。在一般太阳辐射条件下，t_0=60℃，(W/G)=1.67—3.0时，热耗值最低。过多地通入空气是空气饱和蒸馏器动力消耗较大的重要原因。在适当工况下进行操作，所需空气量较小。这样，不但产水量高、热耗值低、系统阻力减少，而且能耗大幅度降低。 模拟试验表明:太阳能空气饱和蒸馏器在太阳辐射日总量4500〔千卡/米~2〕时，每平方米集热器面积，每日可产淡水5—7公斤，所需翅片冷凝器换热面积为0.21〔米~2/时·公斤淡水〕。

Chaotic behavior of pulsating heat pipes

Chaotic behavior of closed loop pulsating heat pipes (PHPs) was studied. The PHPs were fabricated by capillary tubes with outer and inner diameters of 2.0 and 1.20 mm. FC-72 and deionized water were used as the working fluids. Experiments cover the following data ranges: number of turns of 4, 6, and 9, inclination angles from 5 degrees (near horizontal) to 90, (vertical), charge ratios from 50% to 80%, heating powers from 7.5 to 60.0 W. The nonlinear analysis is based on the recorded time series of temperatures on the evaporation, adiabatic, and condensation sections. The present study confirms that PHPs are deterministic chaotic systems. Autocorrelation functions (ACF) are decreased versus time, indicating prediction ability of the system is finite. Three typical attractor patterns are identified. Hurst exponents are very high, i.e., from 0.85 to 0.95, indicating very strong persistent properties of PHPs. Curves of correlation integral versus radius of hypersphere indicate two linear sections for water PHPs, corresponding to both high frequency, low amplitude, and low frequency, large amplitude oscillations. At small inclination angles near horizontal, correlation dimensions are not uniform at different turns of PHPs. The non-uniformity of correlation dimensions is significantly improved with increases in inclination angles. Effect of inclination angles on the chaotic parameters is complex for FC-72 PHPs, but it is certain that correlation dimensions and Kolmogorov entropies are increased with increases in inclination angles. The optimal charge ratios are about 60-70%, at which correlation dimensions and Kolmogorov entropies are high. The higher the heating power, the larger the correlation dimensions and Kolmogorov entropies are. For most runs, large correlation dimensions and Kolmogorov entropies correspond to small thermal resistances, i.e., better thermal performance, except for FC-72 PHPs at small inclination angles of theta < 15 degrees.

Lipase-catalyzed synthesis of biodiesel from acid oil in fixed bed reactor

Acid oil, which is a by-product in vegetable oil refining, mainly contains free fatty acids (FFAs) and acylglycerols and is a feedstock for production of biodiesel fuel now. The transesterification of acid oil and methanol to biodiesel was catalyzed by immobilized Candida lipase in fixed bed reactors. The reactant solution was a mixture of acid oil, water, methanol and solvent (hexane) and the main product was biodiesel composed of fatty acid methyl ester (FAME) of which the main component was methyl oleate. The effects of lipase content, solvent content, water content temperature and flow velocity of the reactant on the reaction were analyzed. The experimental results indicate that a maximum FAME content of 90.18% can be obtained in the end product under optimum conditions. Most of the chemical and physical properties of the biodiesel were superior to the standards for 0(#) diesel (GB/T 19147) and biodiesel (DIN V51606 and ASTM D6751).

Pool boiling heat transfer of ultra-light copper foam with open cells

High speed visualizations and thermal performance studies of pool boiling heat transfer on copper foam covers were performed at atmospheric pressure, with the heating surface area of 12.0 mm by 12.0 mm, using acetone as the working fluid. The foam covers have ppi (pores per inch) from 30 to 90, cover thickness from 2.0 to 5.0 mm, and porosity of 0.88 and 0.95. The surface superheats are from -20 to 190 K, and the heat fluxes reach 140 W/cm(2). The 30 and 60 ppi foam covers show the periodic single bubble generation and departure pattern at low surface superheats. With continuous increases in surface superheats, they show the periodic bubble coalescence and/or re-coalescence pattern. Cage bubbles were observed to be those with liquid filled inside and vented to the pool liquid. For the 90 ppi foam covers, the bubble coalescence takes place at low surface superheats. At moderate or large surface superheats, vapor fragments continuously escape to the pool liquid. Boiling curves of copper foams show three distinct regions. Region I and II are those of natural convection heat transfer, and nucleate boiling heat transfer for all the foam covers. Region III is that of either a resistance to vapor release for the 30 and 60 ppi foam covers, or a capillary-assist liquid flow towards foam cells for the 90 ppi foam covers. The value of ppi has an important effect on the thermal performance. Boiling curves are crossed between the high and low ppi foam covers. Low ppi foams have better thermal performance at low surface superheats, but high ppi foams have better one at moderate or large surface superheats and extend the operation range of surface superheats. The effects of other factors such as pool liquid temperature, foam cover thickness on the thermal performance are also discussed.

近60年我国土壤侵蚀科学研究进展

在系统总结我国近60年土壤侵蚀科学研究取得的成就的基础上,通过分析与整合,重点介绍全国土壤侵蚀时空特征与动态变化、土壤侵蚀过程及其调控机制、黄河泥沙来源与粗泥沙集中来源区的界定、风力侵蚀机制及沙漠化防治、侵蚀环境演变与调控等5个对土壤侵蚀学科发展有重大意义的进展,提出了我国土壤侵蚀学科亟待加强的3个领域。

水肥处理对黄瓜土壤养分、酶及微生物多样性的影响

以津优1号黄瓜为试材,设3个土壤相对含水量水平(50%～60%、70%～80%、90%～100%)和2个肥料追施量(600kgN·hm-2和420kgP2O5·hm-2,420kgN.hm-2和294kgP2O5·hm-2)处理,研究了不同水肥供应对日光温室黄瓜土壤养分、酶活性及微生物多样性的影响.结果表明:土壤中NH4+-N含量随施肥量的增加而提高,随土壤相对含水量的增加而降低;水肥供给的增加有利于提高土壤中速效磷含量和蔗糖酶活性;肥料增加使土壤中蛋白酶活性降低,而水分降低使土壤中脲酶活性提高.土壤中微生物多样性与土壤中养分含量无显著相关性,与土壤脲酶活性呈显著正相关,与蔗糖酶活性呈显著负相关.土壤相对含水量70%～80%、氮肥追施量600kgN·hm-2和420kgP2O5.hm-2处理的土壤养分含量、蔗糖酶、磷酸酶和脲酶活性较高,且土壤中微生物多样性和均匀度显著高于其他处理,土壤生产潜力最优.

水文条件对紫色土坡面土壤侵蚀及养分流失的影响

采用人工模拟降雨试验,研究水文条件对紫色土坡面土壤侵蚀及氮和磷养分流失的影响。试验处理包括2个施肥水平(低肥和高肥水平),4个水文条件(自由下渗、土壤水分饱和、壤中流、壤中流+降雨)和一个降雨强度(60 mm/h,历时60 min)。结果表明:壤中流+降雨和土壤水分饱和条件下的土壤侵蚀量分别是自由下渗条件下的3.1和1.7倍,同自由下渗相比,壤中流、壤中流+降雨和土壤水分饱和条件下,地表径流中NO3-N、HPO4-P的浓度和流失量有显著增加;低肥水平条件下,自由下渗、土壤水分饱和、壤中流和壤中流+降雨地表径流中,NO3-N的浓度分别是0.88、58.90、698.41和87.80 mg/L,对应水文条件下地表径流中,HPO4-P的浓度分别是0.252、0.322、0.811和0.383 mg/L,高肥水平条件下,径流中的NO3-N和HPO4-P的浓度也有相同的趋势;土壤水分饱和条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的27~39和1.3倍,壤中流+降雨条件下,地表径流中NO3-N和HPO4-P的流失量分别是自由下渗条件下的100~114和1.5~1.7倍,同时,壤中流+降雨和土壤...

子午岭60年辽东栎林种子质量与森林更新

辽东栎是我国暖温带落叶阔叶林地带的优势乔木树种之一。通过26年的定位监测,对子午岭辽东栎林种子质量消减、种子萌发与环境条件、实生苗时空分布动态以及对其森林更新的影响等方面进行了初步探讨。结果表明:辽东栎林在子午岭半阳坡、半阴坡和阴坡3种类型中,平均完好种子占种子总数的26.65%;霉变种子占18.72%;动物取食虫蛀种子在阴坡远高于半阴坡和半阳坡,占到种子总数的26.32%;已发芽的种子占其总数的28.31%,且半阴坡>半阳坡>阴坡。每年均有大量种子生产,但在生境与动物的共同作用下,种子数量和质量受到很大影响,多达73.35%的种子失去生命力,直接影响实生苗的形成;地表覆盖物虽能促进种子的快速发芽,但对成苗却是一个物理障碍,影响是负作用的,主要影响因子是地表覆盖物的厚度和含水量;在辽东栎林下虽有一定的实生幼苗分布,但数量极少,平均密度仅为140~120株/hm2,且不同立地条件差异显著,严重影响森林的天然更新。

聚氧化苯乙烯的合成与性能研究

环氧化合物的聚合物被广泛地应用于表面活性剂，增塑剂，涂料和膜等领域。到目前为止，二乙基锌作为络合催化剂的一种，在合成高分子量，高规整度的环氧化合物的均聚产物方面发挥着重要的作用。由于氧化苯乙烯中苯环的存在，使得氧化苯乙烯的开环聚合行为不同于其它的环氧化合物。在迄今为止的催化体系中，聚氧化苯乙烯的数均分子量只能达到800～4000，分子量分布大于100，玻璃化转变为32-40 ℃，且反应通常需要进行10-60天才能得到较高的聚合产率。本工作采用二乙基锌／α-氧化蒎烯为主要催化体系，对氧化苯乙烯的聚合行为、聚合物结构与性能进行了研究，并研究了不同的旋光性催化配体对氧化苯乙烯不对称聚合结果的影响。实验结果表明：一．二乙基锌／α-氧化蒎烯催化体系可以有效地催化氧化苯乙烯的均聚。聚合反应进行72小时即可以有很高的产率（90％），较高的粘度以及分子量（数均分子量大于2.0 * 10~4）。其催化效率远远大于以往的催化体系。二．所得的聚氧化苯乙烯产物为无色透明的塑料状固体，当其对数比浓粘度为1.38dL/g时，玻璃化转变温度为50 ℃，数均分子量可以达到4.07 * 10~4，重均分子量为2.3 * 10~5，分子量分布为5.7。该聚合物的热分解温度为240～250 ℃（5％weight loss，under N_2）。聚合物在空气中长期放置会发生缓慢氧化降解反应而导致聚合物分子量下降。聚氧化苯乙烯在80 ℃下压膜，可以得到无色透明的薄膜，但较脆。该聚氧化苯乙烯溶于氯仿、二氯甲烷、甲苯、苯、四氢呋喃、二氧六环等溶剂，不溶于己烷、甲醇、丙酮等。聚氧化苯乙烯膜耐碱不耐浓硫酸，通常不溶于水，但在沸水中煮过后膜呈不透明状，显示出一定的水溶性。三．催化体系中二乙基锌同α-氧化蒎烯的比例变化对聚合反应的结果有较大的影响。当二乙基锌／α-氧化蒎烯为2:1时，聚氧化苯乙烯的产率、粘度、玻璃化转变温度和分子量都达到最高值，相反当比例为1:3和1:4时，只能得到低分子量的聚合物。二乙基锌与α-氧化蒎烯的预反应时间对于聚合反应的结果没有明显的影响。四．聚合反应的产率随反应时间的增长而增长，表明该体系具有阴离子活性聚合的特点。同时，在相同的单体与催化剂比例中，聚氧化苯乙烯的分子量和产率随着氧化苯乙烯单体的浓度降低而增加。五．聚合反应在80 ℃达到最高值，在室温下产率极低而分子量仍然较高，在100 ℃下却导致分子量下降。聚合物的高温处理结果表明，在聚合体系中同时存在着增长与分解反应，两种反应对于温度的依赖程度不同。六．采用二乙基锌／α-氧化蒎烯、Stilbene oxide、环氧肉桂醇等大位阻的环氧化合物作为催化剂配体同样可以催化氧化苯乙烯得到高分子量的聚合物。催化体系同样适用于环氧丙烷、环氧化环己烯的开环聚合。七．采用旋光α-氧化蒎烯、二苯基乙二醇、环氧肉桂醇等手性化合物为配体可以引发氧化苯乙烯的不对称聚合，其中手性环氧肉桂醇的不对称选择能力最强，所得聚合物的旋光值可达-17.2°。八．通过旋光纯的氧化苯乙烯单体的聚合证实了氧化苯乙烯聚合反应的开环方向为β位，所得的旋光性聚氧化苯乙烯同对应的外消旋体相比，其基本性能并无明显差异，两种聚合物同为无定型结构，其中旋光性聚氧化苯乙烯具有较高的立体规整度和热分解温度，同时在添加了防老剂和紫外线吸收剂的两种聚合物中，旋光性聚氧化苯乙烯具有十分优异的耐老化性能。

铁系催化剂聚合1，3-双烯烃的研究

1，2-聚丁二烯和3，4-聚异戊二烯是制造高性能轮胎的原料。本论文研究了以含磷化合物为第三组份的铁催化剂合成1，2-聚丁二烯和3，4-聚异戊二烯的反应规律：1．以二乙基亚磷酸酷为第三组份的铁催化剂可在己烷中，较高温度（50℃）下聚合1，3-丁二烯。通过控制催化剂组份的配比，可制备间同和无规1，2-聚丁二烯。所得间同1，2-聚丁二烯的1，2-结构含量为91％，间规度为90％；所得无规1，2-聚丁二烯的硫化胶具有优异的抗干、湿滑性能。2．以三苯基磷酸酷为第三组份的铁催化剂是合成高间同1，2一聚丁二烯的高效催化剂。所得聚合物具有高的1，2-结构含量（ca.95％），高的间规度（ca.95％）。聚合物的微观结构与催化剂组成等反应因素无关。3．以二烷基亚磷酸醋为第三组份的铁催化剂可在己烷中，较高温度（50℃）下聚合异戊二烯。二烷基亚磷酸醋中烷基影响聚合活性的顺序为乙基一甲基＞正丁基＞异辛基。所得聚异戊二烯的3，4（含1，2）结构含量保持在60％左右，不受反应条件的影响。4．改性甲基铝氧烷（MMAO）活化的铁催化剂聚合异戊二烯，在相当低的MMAO用量下（Al／Fe=20，摩尔比）即有高的催化活性。溶剂影响聚合活性的顺序为甲苯＞环己烷＞己烷＞二氯甲烷。所得聚异戊二烯的3，4（含1，2）结构含量稳定在60％。

香蕉型分子的真空气相沉积薄膜研究

非手性的香蕉型分子因为独特的形状和极性自组装性能，能形成具有手性结构和特殊光电性能（如铁电性、反铁电性，二次谐波产生效应）的液晶，是近年来有机光电领域中一类非常令人感兴趣的材料。本论文以三环弯核分子间一二（对辛烷氧基苯乙烯基）苯［m-bis（4-p-octoxysryrenyl）benzene，m-OSB］为模型化合物，探索香蕉型分子真空气相沉积薄膜的生长行为。首先，采用示差扫描量热法（DSC）、偏光显微镜、X一射线衍射、透射电子显微镜以及分子模拟等手段表征了m一OSB的体相结构。m-OSB存在两个晶相：相I（T＜66℃）和相11（66oC＜T＜157℃），157oC以上为各向同性态。确定相I为正交晶系，PZI2121空间群，晶胞参数为a＝7．43A，b：6．34A，c＝72．07A，α=β=γ=90°；分子模拟结果显示m一OSB排列成反铁电的层状结构，分子的长轴方向与c轴平行。相n的结构与相I非常相似。这些表征结果为薄膜形态结构的解释提供了依据。然后，采用真空蒸镀的方法制备m-OSB的单层和多层薄膜，用原子力显微镜、透射电子显微镜以及X-射线薄膜反射等手段研究了薄膜形态、结构和薄膜对温度的稳定性。由于香蕉型分子的特殊形状，m-OSB的气相沉积薄膜表现出了特殊的形貌、生长机理和相行为。在单层薄膜生长中，二维岛在40℃以下为圆形或椭圆形的滴状岛，在60℃以上为枝晶状岛，该生长形貌随基底温度的演变与传统的扩散受限凝聚（DLA）理论所预言的结果相反，AFM观察发现滴状岛是从最初沉积的无序膜分解得来的，类似"去润湿"现象；枝晶状岛是从无序膜中成核再通过分子的扩散生长形成的；单层薄膜无论是滴状岛还是枝晶状岛都不稳定，在室温下放置一段时间后均转化为双层的晶体；在多层膜的生长中，观察到了m-OSB形成了高有序、大尺寸的准外延膜。这些在有机气相沉积薄膜生长中都是第一次报道，论文对所观察到的生长现象和相变现象给予了合理的解释。通过对m-OSB气相沉积薄膜的成核和生长过程的系统研究，获得了薄膜形态结构与分子形状和制备参数的关系，对进一步理解有机分子气相沉积薄膜的生长规律和制备高有序的连续薄膜具有重要意义。